Method and apparatus for operating in a discontinuous reception mode employing carrier aggregation

ABSTRACT

Methods and apparatus are described. A long term evolution-advanced (LTE-A) wireless transmit/receive unit (WTRU) includes a transceiver and a processor. The transceiver receives discontinuous reception (DRX) configuration information. The processor, in response to the received DRX information, controls the transceiver to monitor LTE-A physical downlink control channels (PDCCHs) in subframes in a first frequency band during an active time. The processor further, in response to detecting a downlink assignment in an LTE-A PDCCH in the first frequency band during the active time, wherein the downlink assignment indicates a second frequency band and assigned subcarriers within the second frequency band, to receive an LTE-A physical downlink shared channel (PDSCH) K subframes after a transmission of the downlink assignment. The second frequency band is different than the first frequency band.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/238,341, filed Jan. 2, 2019 which issued as U.S. Pat. No. 11,224,017on Jan. 11, 2022, which is a continuation of U.S. patent applicationSer. No. 15/435,943, filed Feb. 17, 2017, which issued as U.S. Pat. No.10,172,087 on Jan. 1, 2019, which is a continuation of U.S. patentapplication Ser. No. 12/817,479, filed Jun. 17, 2010, now Abandoned,which claims the benefit of U.S. Provisional Application Nos.61/218,172, filed Jun. 18, 2009, and 61/233,641, filed Aug. 13, 2009,which are incorporated by reference as if fully set forth herein.

TECHNICAL FIELD

This application is related to wireless communications.

BACKGROUND

Discontinuous reception (DRX) operation in a release 8 (R8) long termevolution (LTE) system is defined by the medium access control (MAC)third generation partnership project (3GPP) specification. Thisfunctionality consists of a set of rules that define when, (i.e., inwhich subframes), a network (i.e., an evolved Node-B (eNB)) may sendcontrol information consisting of downlink (DL) assignments and/oruplink (UL) grants (i.e., shared channel dynamic allocations) to awireless transmit/receive unit (WTRU) using a physical DL controlchannel (PDCCH). The eNB DL assignments and/or UL grants, received bythe WTRU on the PDCCH, signal to the WTRU the existence of DL and/or ULshared channel transmission opportunities. The period of time duringwhich the WTRU monitors the PDCCH for this control information isreferred to as the “active time.” The WTRU may turn off its receivercircuitry on a condition that the PDCCH and other DL physical channelsneed not be monitored, thus resulting in battery savings.

In order to further improve achievable throughput and coverage ofLTE-based radio access systems, and in order to meet the internationalmobile telecommunications (IMT)-advanced requirements of 1 Gbps and 500Mbps in the DL and UL directions, respectively, LTE-advanced (LTE-A) iscurrently under study in the 3GPP standardization body. One improvementproposed for LTE-A is carrier aggregation and support of a flexiblebandwidth arrangement in order to allow DL and UL transmissionbandwidths to exceed 20 MHz in R8 LTE, (e.g., 40-100 MHz).

To support carrier aggregation, it has been proposed that controlinformation carrying a DL assignment pertaining to a given componentcarrier (CC), (over PDCCH), be transmitted over a different DL CC thanthe one that contains the data, (e.g., the physical DL shared channel(PDSCH)). Such an arrangement may be advantageous to the system operatorfor allowing flexibility in the configuration of control channels andthus maximizing capacity. For instance, it allows the transmission ofall PDCCHs from a single CC.

In R8, a time relationship is established based on PDSCH data beingimmediately transmitted in a subframe (i.e., transmission timinginterval (TTI)) of a radio frame after a PDCCH containing acorresponding DL assignment is transmitted in the same subframe. Itwould be beneficial to maintain this time relationship for the scenariowhere PDSCH data and a corresponding PDCCH DL assignment are transmittedon different CCs. However, this scenario potentially requires a higherbattery consumption, since two CCs, (the one containing a PDCCH and theone containing a PDSCH), have to be monitored for a potential DLreception. Thus, efficient DRX methods need to be defined to minimizebattery consumption.

On the other hand, if the PDSCH data is not transmitted in the samesubframe as the PDCCH containing the corresponding DL assignment, higherbattery efficiency may be achieved, since it is known in advance whethera CC needs to be monitored or not for PDSCH. However, breaking the timerelationship creates issues that need to be addressed. If a delaybetween the PDCCH DL assignment and the PDSCH reception is to beintroduced, it is necessary for new procedures to be defined for theWTRU to determine how to find the PDSCH over a period of time.

SUMMARY

A method and apparatus are described for operating a wirelesstransmit/receive unit (WTRU) in a discontinuous reception (DRX) modeemploying carrier aggregation. In one scenario, a physical downlink (DL)shared channel (PDSCH) is received on a DL component carrier (CC) of aparticular serving cell during a cell-specific active time, whereby theDL CC is associated with an uplink (UL) CC. Then, a physical DL controlchannel (PDCCH) is monitored for DL assignments for the particularserving cell, and UL grants for the UL CC, during the cell-specificactive time. In another scenario, a first subset of CCs is configuredfor PDCCH reception, and a second subset of the CCs is not configuredfor PDCCH reception. DRX is applied to at least one CC in the secondsubset based on a PDCCH active time of at least one of the CCs in thefirst subset.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 shows a wireless communication system including a WTRU and aneNB;

FIG. 2 shows an example of the contiguous intra-band carrier aggregationof a plurality of CCs;

FIG. 3 shows a wireless communication system including a WTRU and aneNB; and

FIG. 4 shows the wireless communication system of FIG. 3 in additionaldetail.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of device capable of operating in a wireless environment.

When referred to hereafter, the terminology “evolved Node-B (eNB)”includes but is not limited to a base station, a site controller, anaccess point (AP), or any other type of interfacing device capable ofoperating in a wireless environment.

When referred to hereafter, the terminology “DL CC” may include, but isnot limited to, the DL of a “serving cell,” a “primary serving cell(Pcell),” or a “secondary serving cell (Scell)”.

When referred to hereafter, the terminology “UL CC” may include, but isnot limited to, the UL of a “serving cell,” a “primary serving cell(Pcell),” or a “secondary serving cell (Scell)”.

FIG. 1 shows a wireless communication system 100 including a WTRU 105and an eNB 110, which communicate via a PDSCH 115, a PUSCH 120, a PDCCH125 and a physical UL control channel (PUCCH) 130. The WTRU 105comprises an antenna 135, a receiver 140, a processor 145 and atransmitter 150. The processor 145 comprises a plurality of DRXinactivity timers 155 and a plurality of on-duration timers 160. The eNB110 comprises an antenna 165, a receiver 170, a processor 175 and atransmitter 180. The processor 175 comprises a plurality of DRXinactivity timers 185 and a plurality of on-duration timers 190.

FIG. 2 shows an example of the contiguous intra-band carrier aggregationof a plurality of CCs operating in respective 20 MHz bands.

Active Time Defined on a Per-Carrier Basis

A method of operating in a DRX mode employing carrier aggregation isbased on the concept of active time per CC. In this method, DRXoperation is extended such that “PDCCH active time” is implemented whena WTRU monitors a PDCCH located on a DL CC, and “PDSCH active time” isimplemented when the WTRU monitors a PDSCH located on a DL CC. The WTRUmonitors assignments and/or grants for different CCs using at least onesearch space within a PDCCH, (i.e., specific resource blocks and symbolswhere PDCCH signaling exists for the WTRU).

A “serving cell” is comprised of a DL CC that may be associated with aUL CC. A “cell-specific active time” is defined for each serving cell,including a DL CC configured for PDSCH reception. During thecell-specific active time, the WTRU receives (or buffers) the PDSCH ofthe concerned serving cell for possible assignments received in the samesubframe (i.e., TTI) of a radio frame for this serving cell, andmonitors, in at least one search space specific to this serving cell,the PDCCH of at least one serving cell for assignments for the concernedserving cell, and grants for a UL CC (resource) configured to beassociated to the concerned serving cell, if such a UL CC exists. Theserving cell, for where the WTRU monitors the PDCCH for assignments tothe concerned serving cell, may or may not be the same as the concernedserving cell.

Individual DL CCs may be configured to receive a PDCCH and/or a PDSCHtransmissions. DRX for each active DL CC may be based on PDCCH activetime, PDSCH active time, or a combination of both. DRX may be appliedindependently to each DL CC, and there is no requirement to synchronizeDRX between CCs, although it is possible to force synchronization whenbeneficial.

PDCCH active time is defined for each DL CC that the WTRU is configuredto receive a PDCCH. The PDCCH active time may include the PDSCH activetime of each DL CC that may be assigned from the PDCCH of the DL CC.Each DL CC that may be scheduled has a PDSCH active time. Alternatively,the PDCCH active time may include PUSCH active time, which is a timewhen control information, pertaining to UL CC PUSCH operation from eachDL CC, uses the DL CC for the reception of UL grants and hybridautomatic repeat request (HARQ) feedback. Such a UL CC will be referredto hereafter as an “anchored UL CC”.

The PUSCH active time is defined for each UL CC that the WTRU isconfigured to transmit a PUSCH. The PUSCH active time may include: a)The time while a scheduling request sent on a PUCCH of an anchored UL CCis pending;

-   -   b) The time while a UL grant for a pending HARQ retransmission        may occur and there is data in the corresponding HARQ buffer for        the UL-SCH of an anchored UL CC;    -   c) The time while a CC-specific DRX inactivity timer or other-CC        DRX inactivity timer is running for an anchored UL CC;    -   d) Optionally, the time while a CC-specific on-duration timer is        running for an anchored UL CC (note that such timer may not need        to be defined for a UL CC);    -   e) Optionally (if not already included in a PDSCH active time),        the time while a PDCCH indicating a new transmission addressed        to the cell radio network temporary identifier (C-RNTI) of the        WTRU has not been received after successful reception of a        random access response for the explicitly signaled preamble; and    -   f) Optionally, (if not already included in a PDSCH active time),        the time while the MAC contention resolution timer is running.

The “PDSCH active time” is defined for each DL CC that the WTRU isconfigured to receive a PDSCH. The PDSCH active time may include:

-   -   1) The time while a CC-specific on-duration timer, DRX        inactivity timer, other-CC DRX inactivity timer, DRX        retransmission timer or a MAC contention resolution timer is        running;    -   2) the time while a PDCCH (on same or different CC) indicating a        new transmission addressed to the cell radio network temporary        identifier (C-RNTI) of the WTRU has not been received after        successful reception of a random access response for the        explicitly signaled preamble; and    -   3) Optionally, the PDCCH active time of this same DL CC.

For DRX operation, “cell-specific active time” may include the timewhile a scheduling request (SR) sent on the PUCCH is pending.Cell-specific active time may pertain to a primary serving cell.

For DRX operation, cell-specific active time may include the time whilea UL grant for pending HARQ retransmission may occur, and there is datain the corresponding HARQ buffer for the UL-SCH of the associated UL CC,if such CC is configured.

For DRX operation, cell-specific active time may include the time aPDCCH, indicating a new transmission addressed to the C-RNTI of theWTRU, has not been received after successful reception of a randomaccess response for the preamble not selected by the WTRU. This time maybe included for the cell-specific active time pertaining to the UL CCfrom which the preamble was transmitted, (e.g., associated to theprimary serving cell).

For DRX operation, cell-specific active time may include the time anon-duration timer applicable to the concerned serving cell is running, aDRX inactivity timer applicable to the concerned serving cell isrunning, a DRX retransmission timer applicable to the concerned servingcell is running, or a MAC contention resolution timer is running. Thistime may be included for the cell-specific active time pertaining to aprimary serving cell.

The following definitions of specific DRX inactivity timers andon-duration timers should apply:

-   -   1) DRX inactivity timer for a DL CC: Specifies the number of        consecutive subframes during which the PDSCH of this CC, as well        as the PDCCH of at least one other DL CC providing a DL        assignment for this CC, may be monitored after this timer is        triggered;    -   2) DRX inactivity timer for a UL CC: Specifies the number of        consecutive subframes during which the PDCCH of at least one DL        CC providing a UL grant for this CC may be monitored after this        timer is triggered;    -   3) DRX inactivity timer for a serving cell: Specifies the number        of consecutive subframes during which the cell-specific active        time of this serving cell should be extended after this timer is        triggered;    -   4) Other-CC DRX inactivity timer: Same definition as any of the        DRX inactivity timers described above, except that this timer        (if defined) may only be triggered by a DL assignment or UL        grant (for a new transmission) for a different CC or serving        cell;    -   5) On-duration timer for a DL CC: Specifies the number of        consecutive subframes during which the PDSCH of this CC, as well        as the PDCCH of DL CC(s) providing DL assignments for this CC,        may be monitored at the beginning of a DRX cycle;    -   6) On-duration timer for a UL CC: Specifies the number of        consecutive subframes during which the PDCCH of at least one DL        CC providing a UL grant for this CC may be monitored at the        beginning of a DRX cycle; and    -   7) On-duration timer for a serving cell: Specifies the minimum        number of consecutive subframes during which the cell-specific        active time of this serving cell should exist from the beginning        of a DRX cycle.

The rules for starting and stopping the different timers mentioned aboveare implemented on a per-carrier basis. Thus, the configurationparameters short DRX cycle, long DRX cycle, DRX start offset, as well asthe durations for the on-duration timer, DRX inactivity timer, DRXretransmission timer and DRX short cycle timer may be defined on aper-carrier (or per-serving cell) basis. It is also possible that someof these timers are shared (or are the same) between CCs or servingcells (for instance the on-duration timer may be shared for a set ofCCs). However, the on-duration timer may not need to be defined for ULCCs. In this case, the associated parameters and timers (short DRXcycle, long DRX cycle, DRX start offset, DRX short cycle timer) may notbe defined either, and the DRX retransmission timer and HARQ round triptime (RTT) timers may not need to be defined for UL CCs and UL HARQprocesses respectively.

In addition, the CC-specific DRX inactivity timer may be handled in oneor a combination of the following ways. It is noted that the terminology“triggered” used below may mean initially started or re-started at somelater time.

A CC-specific DRX inactivity timer is triggered for a DL CC, when a newtransmission is received on the PDSCH of this CC, and for a UL CC, whena new transmission is granted for the PUSCH of this CC.

A CC-specific DRX inactivity timer or other-CC DRX inactivity timer istriggered for a DL or UL CC, when a new transmission is received on thePDSCH (or granted for the PUSCH) of another DL (or UL) CC. A subset ofDL or UL CCs that have this property may be pre-signaled by higherlayers.

A CC-specific DRX inactivity timer or other-CC DRX inactivity timer istriggered for a UL CC, a DL assignment or a UL grant (for anytransmission or for a new transmission only) for any CC that isindicated from the PDCCH on the same DL CC that provides grants and HARQfeedback for this UL CC.

A CC-specific DRX inactivity timer or other-CC DRX inactivity timer istriggered for a DL CC, a DL assignment or a UL grant (for anytransmission or for a new transmission only) for any CC that isindicated from the PDCCH on the same DL CC that provides DL assignmentsfor this CC.

It is possible to implement a single DRX inactivity timer or singleother-CC DRX inactivity timer (respectively) per set of CCs using thesame DL CC for PDCCH.

A CC-specific DRX inactivity timer is triggered for a CC (UL only, DLonly, or both UL and DL) when a DL assignment or a UL grant (for anytransmission or for a new transmission only) for any CC is indicatedfrom the PDCCH on any DL CC. It is possible to implement a single DRXinactivity timer or single other-CC DRX inactivity timer (respectively)for all CCs. A subset of DL or UL CCs that have this property may besignaled by higher layers.

An other-CC DRX inactivity timer is triggered for a UL CC, a DLassignment or a UL grant (for any transmission or for a new transmissiononly) for any other CC that is indicated from the PDCCH on the same DLCC that provides grants and HARQ feedback for this UL CC. A subset of DLor UL CCs that have this property may be signaled by higher layers.

An other-CC DRX inactivity timer is triggered for a DL CC, a DLassignment or a UL grant (for any transmission or for a new transmissiononly) for any other CC that is indicated from the PDCCH on the same DLCC that provides DL assignments for this CC. It is possible to implementa single DRX inactivity timer or a single other-CC DRX inactivity timer(respectively) per set of CCs using the same DL CC for PDCCH. A subsetof DL or UL CCs that have this property may be signaled by higherlayers.

An other-CC DRX inactivity timer is triggered for a CC (UL only, DLonly, or both UL and DL) when a DL assignment or a UL grant (for anytransmission or for a new transmission only) for any other CC isindicated from the PDCCH on any DL CC.

A CC-specific DRX inactivity timer or other-CC DRX inactivity timer istriggered for a DL or UL CC when a new transmission is received on thePDSCH (or granted for the PUSCH) of another DL (or UL) CC, with theadditional condition that the on-duration timer for that other CC isrunning. A subset of DL or UL CCs that have this property may bepre-signaled by higher layers.

An other-CC DRX inactivity timer is triggered for a CC (UL only, DLonly, or both UL and DL) when a DL assignment or a UL grant (for anytransmission or for a new transmission only) for any other CC isindicated from the PDCCH on any DL CC, with the additional conditionthat the on-duration timer for that DL CC is running. A subset of DL CCsthat have this property may be pre-signaled by higher layers.

A serving cell-specific DRX inactivity timer is triggered when a newtransmission is received on the PDSCH, or a new transmission is grantedfor the PUSCH for this serving cell.

A serving cell-specific DRX inactivity timer or other-CC DRX inactivitytimer is triggered when a new transmission is received on the PDSCH, ora new transmission is granted for PUSCH for a different serving cell. Asubset of serving cells that have this property may be configured byhigher layers.

An other-CC DRX inactivity timer is triggered when a new transmission isreceived on the PDSCH, or a new transmission is granted for PUSCH for adifferent serving cell. A subset of serving cells that have thisproperty may be configured by higher layers.

It is possible to implement a single DRX inactivity timer or a singleother-CC DRX inactivity timer (respectively) for all CCs.

In any case described above that includes the starting or re-starting ofthe DRX inactivity timer or other-CC DRX inactivity timer, a delay of afew subframes may be required between the triggering event and theactual start or re-start of the DRX inactivity timer or other-CC DRXinactivity timer. This allows some wake-up time for activating thereception on the concerned CC.

DRX timers (cycles, on duration, inactivity, retransmission) may beoptimized for traffic requirements on each DL and/or UL CC they areconfigured for. Each individual UL or DL CC not carrying PDCCH may beconfigured so that the required reception periods (PDSCH or PUSCH activetimes) are included in a subset of the combined reception periods (PDCCHactive time) on the associated CC carrying a PDCCH.

Furthermore, the following rules may apply regarding the transmission ofchannel quality indicator (CQI)/precoding matrix index (PMI)/rankindicator (RI) and sounding reference symbol (SRS), whereby CQI/PMI/RIpertaining to the DL-SCH of a CC is not reported when this CC is not inPDSCH active time, or when the corresponding serving cell is not incell-specific active time, and SRS pertaining to the UL-SCH of a UL CCis not reported when this CC is not in PUSCH active time, or when thecorresponding serving cell is not in cell-specific active time.

Active Time Defined on a Per-Carrier With PDCCH Basis

Alternatively, there may be just PDCCH active time defined for each DLCC that has PDCCH configured. The short DRX cycle, long DRX cycle, andthe DRX start offset parameters, as well as the durations for theon-durationTimer, DRX inactivity timer, DRX retransmission timer, andDRX short cycle timer are defined just for DL CCs that are configuredfor PDCCH reception. The rules for starting and stopping these timersmay be similar to the previously known conventional rules, except thatthere is an independent PDCCH active time for each DL CC configured forPDCCH reception. In addition, conventional triggering rules pertainingto UL transmissions may now be applied, for each DL CC configured forPDCCH reception, only to those UL transmissions on UL CC that arereceiving grants and HARQ feedback from this DL CC.

Other DL CCs without PDCCH that may have PDSCH transmissions assignedfrom a particular CC carrying PDCCH may apply the same DRX defined bythe PDCCH active time of this CC carrying PDCCH. This solution avoidsthe need to maintain DRX timers on each DL CC without PDCCH and on eachUL CC, but eliminates the possibility to optimize DRX timers for eachCC.

In the case there are several CCs configured to receive a PDCCH that mayprovide DL assignments for a CC which does not have PDCCH, the DRX forthis CC is the sum of PDCCH active times of the CCs which have PDCCH andmay provide PDSCH assignments for this CC. Alternatively, the PDCCHactive time of one “primary” CC out of the several CCs configured toreceive a PDCCH that may provide DL assignments for a given CC, may beselected to define the PDSCH active time for this CC.

Active Time Defined on a Per-Carrier with PDCCH and Delayed DL SCHReception

PDSCH transmissions are currently not delayed relative to PDCCHassignment of this transmission. Therefore when PDCCH on one CC (CC #x)may allocate PDSCH for another CC (CC #y), reception on the other CC (CC#y) may be enabled even when there is no assignment on this CC (CC #y)since the reception of the PDSCH and common reference symbols on theother CC (CC #y) may start before the PDCCH is completely received onone CC (CC #x). To allow CC with only PDSCH reception configured to wakeup only when the corresponding PDCCH assignment was received on anotherCC, PDSCH transmission may be delayed relative to PDCCH to allow foractivation of PDSCH CC reception and PDCCH processing time.

Alternative, PDSCH transmissions may be delayed k subframes from PDCCHassignment when PDSCH transmission occurs on a CC that is different fromthe CC the PDCCH assignment was received on. Furthermore, all PDSCHtransmissions may be delayed relative to a PDCCH assignment, regardlessof which DL CC is assigned for an R10 WTRU.

With either of these approaches, DRX on CCs that do not have PDCCHconfigured do not require DRX active time defined by existing DRXtimers, (e.g., DRX cycle, on-duration, inactivity, retransmissiontimers). The WTRU is not required to always receive on a CC withoutPDCCH during PDCCH active time on other CCs.

DRX on CCs without PDCCH may be governed by the PDCCH assignmentsreceived for this WTRU on other CCs. Reception is only enabled when aPDCCH assignment has been received.

Since PDSCH transmission is delayed by k subframes, UL HARQ feedback isalso delayed by k subframes. Relative to PDCCH assignment HARQ feedbackwill be received at k+4 subframes. This potentially results in feedbackcollision between assignments with delayed PDSCH and feedback acrossCCs, and non-delayed PDSCH and feedback when a PDCCH and a PDSCH are onthe same CC. There are several potential solutions, including delayPDSCH and feedback even when on same CC, or aggregate feedback with thesame mechanism used for more DL CCs than UL CCs.

Due to the delayed DSCH transmission additional DL HARQ processes willbe required. Currently there is an eight (8) subframe HARQ process RTT.With the k subframe delayed DSCH, the DL HARQ RTT may be increased by ksubframes. In order to allow for continuous PDSCH transmission,additional HARQ processes may be required.

One alternative to increasing the DL HARQ RTT and number of DL HARQprocesses may be to reduce the PDCCH and/or PDSCH processing time. Forexample if k=2 with PDCCH processing reduced to 2 subframes and enablingreception PDSCH reception across CCs reduced to 2 subframes the existingHARQ RTT and number of HARQ processes may be maintained.

Another consideration is UL feedback collisions in the time domainbetween WTRUs. A R8 WTRU without delay is scheduled k subframes after arelease 10 WTRU with delay. Several solutions may be considered for thisconflict including UL CCs are assigned either to further delayedfeedback or not. All WTRUs configured on a given UL CC will either havefurther delayed feedback or not. Alternatively, a smart eNB schedulermay minimize the switching points between further delayed feedback andnot further delayed feedback. When switching between feedback latenciesoccurs, the scheduler may enforce scheduling gaps to avoid feedbackcollision.

Alternatively, subframe time boundary of CCs without PDCCH allocation(CC #y) may be shifted in time, such as the reception of the PDSCH andthe common reference symbols may start after the PDCCH reception on theother CC (CC #x) is completed (up to symbol #3) and processed. Forexample, symbol #0 of CCs without PDCCH allocation may be transmitted atthe same as symbol #8 of CCs with PDCCH. This may allow the WTRU toprocess the PDCCH in 4 symbols or 4/14 of a subframe. With thisapproach, the requirement in terms of PDSCH processing time to send theUL HARQ feedback may not be impacted significantly relative to R8,(i.e., the processing time may be reduced by only 5/14 of a subframe).

Referring again to FIG. 1, the processor 145 in the WTRU 105 comprisesat least one DRX inactivity timer 155 and at least one on-duration timer160. The WTRU 105 operates in a DRX mode employing carrier aggregation,receives DL transmissions or transmits UL transmissions, during anactive time, on a CC that is not configured for PDCCH reception,monitors a PDSCH for shared channel dynamic allocations including a DLassignment or a UL grant, and applies DRX to the CC based on PDSCHactive time or PUSCH active time.

Alternatively, the processor 145 in the WTRU 105 operates in a DRX modeemploying carrier aggregation, receives DL transmissions or transmits ULtransmissions, during an active time, on a plurality of CCs where afirst subset of the CCs are configured for PDCCH reception and a secondsubset of the CCs are not configured for PDCCH reception, and appliesDRX to at least one CC in the second subset based on a PDCCH active timeof at least one of the CCs in the first subset.

FIG. 3 shows an LTE wireless communication system/access network 200that includes an evolved-universal terrestrial radio access network(E-UTRAN) 205. The E-UTRAN 205 includes several eNBs 220. A WTRU 210 isin communication with an eNB 220. The eNBs 220 interface with each otherusing an X2 interface. Each of the eNBs 220 interface with a mobilitymanagement entity (MME)/serving gateway (S-GW) 230 through an S1interface. Although a single WTRU 210 and three eNBs 220 are shown inFIG. 3, it should be apparent that any combination of wireless and wireddevices may be included in the wireless communication system accessnetwork 200.

FIG. 4 is an exemplary block diagram of an LTE wireless communicationsystem 300 including the WTRU 210, the eNB 220, and the MME/S-GW 230. Asshown in FIG. 4, the WTRU 210, the eNB 220 and the MME/S-GW 230 areconfigured to perform DRX based on per carrier active time as describedabove.

In addition to the components that may be found in a typical WTRU, theWTRU 210 includes a processor 316 with an optional linked memory 322, atleast one transceiver 314, an optional battery 320, and an antenna 318.The processor 316 is configured to perform DRX based on per carrieractive time as disclosed above. The transceiver 314 is in communicationwith the processor 316 and the antenna 318 to facilitate thetransmission and reception of wireless communications. In case a battery320 is used in the WTRU 210, it powers the transceiver 314 and theprocessor 316.

The WTRU 210 is configured to perform a DRX operation. The transceiver314 is configured to monitor a DL CC for the reception of a PDCCH, andthe processor 316 is configured to determine a PDCCH active time foreach DL CC that the WTRU 210 is configured to receive the PDCCH. Thetransceiver 314 may also be configured to monitor a DL CC for thereception of a PDSCH, and the processor 316 is configured to determine aPDSCH active time for each DL CC that the WTRU 210 is configured toreceive the PDSCH.

In addition to the components that may be found in a typical eNB, theeNB 220 includes a processor 317 with an optional linked memory 315,transceivers 319, and antennas 321. The processor 317 is configured toperform a method of DRX based on per carrier active time as disclosedabove. The transceivers 319 are in communication with the processor 317and antennas 321 to facilitate the transmission and reception ofwireless communications. The eNB 220 is connected to the MME/S-GW 230,which includes a processor 333 with an optional linked memory 334.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a transceiver; and a processor operatively connected to thetransceiver, the transceiver and the processor configured to receiveinformation indicating a first inactivity timer, a second inactivitytimer, at least one first component carrier associated with the firstinactivity timer, and at least one second component carrier associatedwith the second activity timer; and the transceiver and the processorconfigured to monitor physical downlink control channels (PDCCHs) forthe at least one second component carrier based on the second inactivitytimer and to monitor PDCCHs for the at least one first component carrierbased on the first inactivity timer.
 2. The WTRU of claim 1, wherein thereceived information is received by higher layers signaling.
 3. The WTRUof claim 1, wherein the transceiver and the processor configured toreceive a PDSCH assignment in one of the monitored PDCCHs and to receivethe PDSCH at a time delayed with respect to the one PDCCH.
 4. The WTRUof claim 3, wherein the transceiver and the processor configured totransmit hybrid automatic repeat request (HARQ) feedback at apredetermined time interval after receipt of the PDSCH.
 5. The WTRU ofclaim 3, wherein the PDSCH assignment is for a different componentcarrier than a component carrier that the one PDCCH was received.
 6. TheWTRU of claim 1, wherein the at least one second component carrier is aplurality of component carriers, and wherein the at least one firstcomponent carrier is a plurality of component carriers.
 7. A methodimplemented by a wireless transmit/receive unit (WTRU) comprising:receiving information indicating a first inactivity timer, a secondinactivity timer, at least one first component carrier associated withthe first inactivity timer, and at least one second component carrierassociated with the second activity timer; and monitoring physicaldownlink control channels (PDCCHs) for the at least one second componentcarrier based on the second inactivity timer and monitoring PDCCHs forthe at least one first component carrier based on the first inactivitytimer.
 8. The method of claim 7, wherein the received information isreceived by higher layers signaling.
 9. The method of claim 7, furthercomprising receiving a PDSCH assignment in one of the monitored PDCCHsand to receive the PDSCH at a time delayed with respect to the onePDCCH.
 10. The method of claim 9, further comprising transmitting hybridautomatic repeat request (HARQ) feedback at a predetermined timeinterval after receipt of the PDSCH.
 11. The method of claim 9, whereinthe PDSCH assignment is for a different component carrier than acomponent carrier that the one PDCCH was received.
 12. The method ofclaim 7, wherein the at least one second component carrier is aplurality of component carriers, and wherein the at least one firstcomponent carrier is a plurality of component carriers.